How does a power saver work?

[blastronics]

anybody...
i have seen power saver in the market, the one that only plugs into outlet and reduces your bill by up to 20%.
i wonder how this works.
any body can discuss this ?

:idea:

 

[Manoj Mulajkar]

Re: power saver

Only way to save power is to reduce reactive power .
Reactive Power =VIsinΦ
Φ=phase difference between Voltage and current.
Active Power =VICosΦ

If we reduce Φ, CosΦ (Power factor) will increase in turn Active power increases and reactive power decreases. It will lead to power saving.

It is only theory for power saving. In industries this is achieved by capacitor bank, and thyristorised control (if sinusoidal output not required).

I think power saving is possible in case of inductive load only, where is chance for Power factor improvement.

For resistive load, Total Power = Active Power = VI as CosΦ is unity (max).
If anybody claiming poer saving in resistive load, then they are cheating you by reducing voltage in turn even active power is getting reduced. I can challange anybody whoever claiming power saving in case of resisitve load